The invention concerns a rotary embossing machine in accordance with the features of the indepenent claim.
These rotary embossing machines are used to apply embossing sheet sections onto an endless material web. The embossing sheet sections are sections of a heat-sealing sheet having structured or smooth surfaces and can also have a hologram and a thermally activatable fusion adhesive on the rear side. During application thereof, the embossing sheet section is transferred from the sheet web and glued onto the material web or the remaining sheet backing is removed from the glued section. During or after gluing, a pattern can be embossed into the surface of the sheet. These machines can also be used to apply holograms onto material webs wherein, in particular, the temperature of the embossing tool and of the embossing sheet should be precisely regulated and the tension of the embossing sheet must be exactly controlled to prevent destruction of the hologram.
The embossing sheet advance, which is usually also an endless sheet, must be exactly controlled for exact positioning of the embossing sheet sections and for minimizing embossing sheet waste. The embossing sheet advance is usually less than the transport speed of the material web. The location where the embossing sheet section is applied must correspond to the imprint in the material web. Finally, for holograms, the section of the embossing sheet to be embossed must be precisely oriented relative to the embossing stamp to prevent destruction of the hologram, to transfer it into the correct position, and to fix it on the material web.
Conventional rotary embossing machines have the associated problem that the transport speed of the embossing sheet is adjusted in order to minimize waste. This is associated with a relatively large degree of effort.
It is therefore the underlying purpose of the invention to provide a rotary embossing machine with which the embossing sheet and also the material web are treated with great care, wherein the transport speed of the embossing sheet can be adjusted in a simple fashion.
This object is achieved with a rotary embossing machine having the features of the independent claim. Advantageous further developments can be extracted from the dependent claims.
The inventive rotary embossing machine ensures that the material web and also the embossing sheet provided as an endless web are transported only in one direction and do not exert any back and forth motion, i.e. the transport direction does not change. The embossing device, which rotates in a direction opposite to that of the counter pressure cylinder, contains at least one embossing unit with each embossing unit having its own complete supply of embossing sheet for that embossing unit. The embossing sheet is transported by a transport means provided in the embossing unit such that a new embossing sheet section is continuously supplied while minimizing sheet waste. This can be effected in a gentle fashion through slow advance.
The rotary motion of the embossing device imparts a speed to the embossing sheet section which corresponds to that of the material web such that the section can be easily transferred from the embossing tool to the material web. Directly after transfer of the embossing sheet section, the embossing sheet is gently further transported and a new embossing sheet section is provided. It is important that the embossing device precisely matches the speed of the embossing sheet to the speed of the material web. The embossing sheet itself is at rest in the embossing device during the embossing process.